1. Field of the Invention
The present invention relates generally to a process for producing deep-drawn containers and, more particularly, to a process for producing deep-drawn containers in the form of cups, pans or the like, which are formed of two material components.
2. Description of the Prior Art
Deep-drawn containers made from deep-drawable plastic foils, especially in the form of cups for packaging food, such as yogurt, cottage cheese, and other milk products and also ready-to-serve dishes or the like, are generally known. It is also known, depending on the desired make-up of the packaging, for example according to DAS No. 2,065,713, to introduce prior to deep-drawing in the deep-drawing mold a banderole with legends and/or illustrative pictures and to seal them at the same time. After filling, such deep-drawn packagings are covered with a metal foil.
The bottom area of the cups or containers is excluded from this operation in the prior art process so that this area which, as a rule, because of the special character of the deep-drawing operation, is formed especially thin, remains unreinforced and is not very stable. Since the bottom remains uncovered, an overhead display arrangement of the goods cannot be considered as there is no "all-around-decoration."
Basic to the present invention is the problem of providing a process by way of which the outer surface of the container can be completely covered, i.e. especially the bottom area, it being an object of this invention to permit, by way of such a process, the production of deep-drawn containers having a circumferentially applied thin aluminum foil which otherwise is no longer deep-drawable. The process of the present invention, as well as the product made thereby, has been desired for some time because the prior art deep-drawn plastic packages do not comply with the requirements for an absolute tightness relative to flavor, water vapor, oxygen and light, thereby limiting the storage stability of food packed therein. Packages in line with these requirements, it is true, are known. However, they have been drawn from a relatively thick aluminum foil, thus involving a substantial mechanical expenditure and with the depth of such container being relatively shallow.
The problem is solved according to the present invention by means of a process of the aforementioned type in that connected to the deep-drawable component, prior to the introduction thereof into the deep-drawing mold and at intervals corresponding to the feeding cycle, there is provided a bottom blank corresponding to the bottom shape of the container to be produced but of slightly larger dimensions. The bottom blanks may be made, for example, of a thin, non-deep-drawable aluminum foil and are secured to the deep-drawable component from the bottom by heat sealing. During introduction of the deep-drawable component into the deep-drawing mold the bottom blanks, with the adhesive still hot, are placed precisely in the center of the mold and the bottom blank during deep-drawing in the deep-drawing mold is held from the bottom, for example by means of a die.
In this manner, first a "roundabout decoration" and also a reinforcement of the bottom area can be achieved, with the problem of covering the suction opening in the deep-drawing mold, which would arise if the bottom blank were simply placed into the mold being avoided and solved in a most simple manner.
Conversely, this process permits, when using for the components to be cemented, i.e. a side wall banderole and a bottom blank, a thin aluminum foil, to produce deep-drawn containers complying with all tightness requirements, especially cups of a substantial depth, which hitherto, has not been possible.
The problem of covering the suction opening can also be solved differently. In addition to the banderole a bottom blank, the edge of which prior to insertion is radially folded and bent upwardly, is inserted into the deep-drawing mold so that the bottom edge of the banderole is positioned between the upwardly bent edge and the mold wall.
Through the radial folding venting openings are provided between the banderole and the inserted bottom blank through which the drawn off air can escape. This process variant provides the additional advantage that the upwardly bent and pre-folded edge better abuts to the bottom banderole rim and establishes a connection therewith.
Concerning the covering of the upper gusset or flange of the container, the two modes of operation may be so carried out that the blank web and the bottom blanks are heat sealed to the deep-drawable component and are introduced along therewith into the deep-drawing mold.
With respect to the product produced according to the process of this invention it should be noted that for protection the side wall banderole of the deep-drawn container covers the rim bent upwardly during deep-drawing of the bottom blank and which was heat sealed prior to deep-drawing and is heat sealed therewith. Furthermore, the side wall banderole of the deep-drawn container covers the rim bent dowardly during deep-drawing of the concentrial edge blank or ring-like member and is heat sealed therewith.
The apparatus for carrying into effect the process and for the preparatory production of the deep-drawing foil, respectively, is most simple and can either be associated in a suitable manner to the deep-drawing machine or can be operated independently thereof. However, in the latter case, the component blanks must precisely correspond to the working and intake cycle of the deep-drawing machine to which the latter are applied.
In principle, such an apparatus is a punch combined with means to cyclically sealing the blanks with heat sealing adhesive on or to the deep-drawing foil.
The process of the invention, the container produced according thereto and an apparatus for carrying into effect the process will now be described with reference to the graphic illustration of examples of several embodiments.